Cam follower for the variable actuation of a gas-exchange valve of an internal combustion engine

Abstract

The cam follower has a roller, which is movable, between a first axial position and a second axial position and which alternately transmits elevations, which are different from one another. The cam has a cylinder-piston unit, which has a pressure medium space for moving the roller from the first axial position into the second axial position, and a spring means for moving the roller from the second axial position into the first axial position. The piston of the cylinder-piston unit is the roller and the roller has an end wall, which delimits the pressure medium space, and an annular collar which extends from said end wall and whose outer lateral surface serves as a cam pick-off surface. The inner lateral surface of the annular collar surrounds an outer section of the cylinder of the cylinder-piston unit.

1. Cam follower for a variable actuation of at least one gas-exchange valve of an internal combustion engine, comprising:
 a roller axle; 
 a roller, which is mounted so as to be movable in a roller bore relative to the roller axle between a first axial position and a second axial position and which alternately transmits elevations, which are different from one another, of two cams which are arranged adjacently on a camshaft to the gas-exchange valve; 
 a cylinder-piston unit, which forms a pressure medium space, for moving the roller from the first axial position into the second axial position; and 
 a spring means for moving the roller from the second axial position into the first axial position, 
 wherein a piston of the cylinder-piston unit is the roller itself, with the roller having an end wall, which delimits the pressure medium space, and an annular collar which extends from the end wall and whose outer lateral surface serves as a cam pick-off surface and whose inner lateral surface surrounds an outer lateral surface of an outer section of a cylinder of the cylinder-piston unit in a low-leakage or pressure-medium-tight manner, and 
 wherein the cam follower is a lever which is pivotably mounted in the internal combustion engine and which has side walls which run spaced apart from one another, with the cylinder-piston unit and the spring means being arranged entirely between the side walls. 
 
     
     
       2. Cam follower according to  claim 1 , wherein the end wall of the roller has, on the side facing away from the pressure medium space, at least one cylindrical recess for the support of the spring means, which is embodied as at least one coil pressure spring, on the roller. 
     
     
       3. Cam follower according to  claim 1 , wherein the cylinder is rotatably mounted on the roller axle and is axially supported against one of the side walls via a sliding disk. 
     
     
       4. Cam follower according to  claim 1 , wherein the roller is mounted by means of a tubular inner section of the cylinder on the roller axle, with the inner lateral surface of the inner section serving for mounting the cylinder on the roller axle, and with the roller bore being mounted in a movable fashion on the outer lateral surface of the inner section. 
     
     
       5. Cam follower according to  claim 4 , wherein the inner section of the cylinder is fixed to the roller axle. 
     
     
       6. Cam follower according to  claim 4 , wherein the cylinder has, at that end of the inner section which is remote from the pressure medium space, a radially outwardly extending flange which supports the spring means at the roller axle side. 
     
     
       7. Cam follower according to  claim 6 , wherein the flange serves as an axial plain bearing for the spring means. 
     
     
       8. Cam follower according to  claim 4 , wherein, for conducting pressure medium, the roller axle is of hollow cylindrical design, has a first pressure medium bore which is connected to a first pressure medium duct which runs in the cam follower, and has a second pressure medium bore which is connected to the pressure medium space by means of a second pressure medium duct which runs in the inner section of the cylinder. 
     
     
       9. Cam follower according to  claim 8 , wherein the first pressure medium bore and the first pressure medium duct are connected to one another by means of a first encircling groove and/or in that the second pressure medium bore and the second pressure medium duct are connected to one another by means of a second encircling groove.